Di-pyridyl aliphatic alkylene polyamine poly acids



DI-PYRIDYL ALIPHATIC ALKYLENE POLYAMINE POLY ACIDS Frederick C. Bersworfl East Orange, N. .L, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Original application September 2, 1950,

Serial No. 183,079. Divided and this application ctober 30, 1952, Serial No. 317,840

Claims. (Cl. 260-295) This invention relates to chelating agents for metal ions in aqueous solution and has for its object the provision of a water soluble aliphatic alkylene polyamino poly acid which forms stable water soluble salts and chelate compounds with basic compounds and metal ions in aqueous solution.

Another object is to provide an aliphatic alkylene polyamine poly acid which contains pyridyl substituent groups which are water soluble in water and which form water soluble salts and metal chelate compounds with metal ions in aqueous solutions.

Still another object is to provide a di-pyridyl aliphatic alkylene polyamino poly acid which is water soluble.

Other objects will be apparent as the inv ention is more fully hereinafter disclosed.

In accordance with these objects I have discovered that when two (2) of the amino hydrogens of an aliphatic alkylene polyamine are displaced by an alkylene group of from 1 to 12 carbon atoms in which group is substituted a pyridyl group and the remaining amino hydrogens by acetic acid or a homologue acid, the resulting dipyridyl substituted aliphatic alkylene polyamino polyacetic acid is water soluble and forms water soluble salts With bases, such as metal oxides, hydroxides and carbonates and forms metal chelate compounds with metal ions in aqueous solution which are soluble and resistant to decompositions by normal precipitating agents therefor.

The general formula for the di-pyridyl aliphatic alkylene polyamine poly acids of th Present invention is:

A LN/ Rl l( alkyle ne- \N where A=CH2-COOH or a higher homologue acid; R=an aliphatic carbon chain of from one to twelve carbon atoms; alkylene=CH2-CHg, CH-CH3-CH2 and CH2'CH2-CH2; and 11:1, .3 and 4.

In general, my discoveries indicate the following remarkable facts concerning these di-pyridyl compounds:

(1) That for all stated values of A and n, and for R=CI-I2, it has been found that the chelating agents are quite water soluble;

(2) That the metal chelates of (l) are also quite soluble in water;

Th t a the n mb r f carbon a oms in E r s, bo h h ch l ting ag nt a d s the meta chelate become less soluble in Water but at the sametime become emulsifying and surface active. For example, when R=(CH2)1zn.=1; and A=acetic acid, the product is a good foaming and emulsifying agent, and sequesters heavy metals to form chelates which are also good foaming and emulsifying agents. Its chelates with heavy metals ofthe transition series of the periodic table are very stable. However, this chelating agent has little aflinity for alkaline earth metals, and combine only weakly with the rareearths;

2,751,390 Patented June 19, 1956 (4) I have found that increasing 7; in general increases Water solubility and chelating power for heavy metals; 0 i

(5) I have also found that when alkylene is ethylene and propylene, the stability of metal chelates is higher than when it is trimethylene;

(6) Also, the stability of the chelates is greater for A=acetic acid than for A=propionic acid;

(7) When A=propionic acid and alkylene=trimethylene simultaneously, chelating power is in general the w a est, an st onge t when A= et c acid and a k ene=ethyleue;

(8) In the case of the derivatives of ethylene diamine diacetic acid (alkylenezethylene, A=CH2-COOH, and 21:1) I have found remarkable differences for combination with various metal ions for the chelates resulting from a change in R. Thus for the structure:

The chelating power may be varied greatly by changing R. When R=O, the copper chelate is very stable, and, while the cobalt and nickel chelates are also quite stable, and not dissociated in aqueous solution, their stabilities are relatively much lower than that .of 11. copper chelate. A change of R to CH2- profoundly affects the chemical properties of the compound. The stability of the copper chelate is increased somewhat. On the other hand, the stabilities of the nickel and cobalt chelates are so great that they are now more stable than the copper chelate. For the equilibrium:

M +KeT MKe where M=Co or Ni; and Ke is the vchelating agent described above for which R=CH2, I have found for the equilibrium constant:

(ll K 9) phatic nitrogen and the pyridine ring.

K equilibrium 10.

Example 1 Five moles of ,a-arnino pyridine was carefully carboxymethylated with five moles of sodium cyanide and 5 moles of formaldehyde at room temperature in a rapidly stirred aqueous solution at pH 10.5, according to the process described in my Patent No. 2,407,645. After complete removal of ammonia by distillation, the reaction solution containing the pyridyl acetic acid Na salts was treated without further purification with 2.5 moles ethylene dichloride and heated for ten hours at C. in a rapidly stirred pressure vessel. The reaction product was primarily a pale yellow solution of ethylene diamine N,N bis a-pyridyl- N,N' diaeetic-acid and sodium chloride. The pure product may be isolated as the dihydrochloride, which i s y purifi d byt ct ona a r a izatiqn or a the coppersalt The structural formula of the acid eonforms to thefollowing:

CHz-C O O'HZ CHe-C OOH 3 Example 11 Two moles of anirno u-picoline are treated with two moles NaCN and formaldehyde as in Example I. The reaction product (sodium salt) is then treated with ethylene dichloride as in Example I. The product is believed to have the formula:

CHz-COOH CHTCOOH It may be crystallized as the acid from hydrochloric acid solutions.

Example 111 Two moles of chloro a. picoline (having chlorine in the side chain) are treated with one mole of ethylene diamine, N,N' dipropionic acid in a rapidly stirred aqueous solution buffered to about pH 9 at about 50 C. After twelve (12) hours the reaction was considered complete and a crystallizable product was obtained on acidification with HCl which is believed to have the formula:

CHrCHz-COOH CHa-CHa-CO OE Example IV Ten moles of B-amino-fi-ethylpyridine was treated by slow addition of two moles of trimethylene chloride (ethylene chloride may be used to form the ethylene diamine derivative) at about 50 C. over a period of 2 hours, followed by heating in a pressure vessel for 8 hours at 100 C. The reaction mixture was then treated with four moles of caustic soda, and the excess B-amino-6-ethylpyridine was recovered by distillation. The residue was separated from the sodium chloride which separated, dissolved in 4 parts of water by volume, and treated with four moles of sodium cyanide and four moles of formaldehyde as described in my U. S. Patent No. 2,407,645. On acidification with hydrochloric acid a crystalline product was isolated which is believed to have the formula:

CHz-GOOH CHTCOOH N CH:- CHQ'N-GHrCHr GHz-NCH H3- N Example V Two moles of Z-acetyl pyridine are treated with one mole of diethylene triamine to give the Schiff base:

This material is prepared in aqueous solution and is not isolated. It is then carefully reduced catalytically at moderate temperatures (somewhat above room temperature) with a promoted nickel catalyst to the di(pyridylalkyl) diethylene triamine derivative. The reaction was stopped after two moles of hydrogen was absorbed. The aqueous product was then filtered and treated directly according to my U. S. Patent No. 2,407,645 with 3 moles of NaCN and 3 moles of formaldehyde to give, after acidification, a crystalline product believed to have the following composition:

CHz-COOH CHrOOOH CHz-COOH The following reactions are examples of the type of chelates formed with heavy metals:

Cu l-compound of Example II O-C vv GHQ Thus it can be seen that the chelating agent provides four bonds for copper (usually considered the maximum for copper) but that six bonds are-available for combining with the other transition metals. It is felt that this offers a qualitative interpretation as to the relatively stronger chelation with Co and Ni than is usual for chelating agents. Another factor which is believed important is that four nitrogens are here available for bond formation whereas in ethylene diamine tetra acetic acid, a more common and better known chelating agentonly two donor nitrogens are present.

In the case of other chelating agents of this disclosure which have weaker tendencies for combining with metals, it is felt that the active groups may not be as favorably situated for forming strong chelate compounds with metals. Thus the observations given above on relative stabilities may serve as a guide for further understanding the structural requirements favorable for combination of organic reagents with metals. 7 1

This application is a divisional application of application Serial No. 183,079 filed September 2, 1950, andnow abandoned.

Having hereinabove described the present invention generically and specifically and given several specific examples thereof, it is believed apparent that the same may be widely varied without essential departure therefrom and all such modifications of and departures from the same are contemplated as may fall within the scope of the following claims: 1

What I claim is:

l. A compound which is a member of the group consisting of compounds conforming to the following structural formula:

2, 3 and 4; and the alkali metal and acid addition salts of said compounds.

2. The compound conforming to the structural formula:

CHa-COOH CHz-COOH 'N/-CH2NCH2-CH:NCH 3. The compound conforming to the structural formula:

CHTOHz-GOOH CHrOHz-COOH H l 11 Cl 4. The compound conforming to the structural formula:

5. The compound conforming to the structural formula:

OHz-COOH CHz-COOH CHz-COOH References Cited in the file of this patent Sharp: J. Chem. Soc., 1938, pp. 1191-3. Whitmore et al.: JACS, vol. 67, pp. 393-5 (1945). 

1. A COMPOUND WHICH IS A MEMBER OF THE GROUP CONSISTING OF COMPOUNDS CONFORMING TO THE FOLLOWING STRUCTURAL FORMULA: 